Flashing lanterns include both flashing beacons and strobe lights. Flashing beacons typically have incandescent or halogen bulbs as their light source, while strobe lights normally incorporate xenon flash tubes. Strobe lights and flashing beacons are used primarily on moving vehicles, such as materials-handling vehicles, construction vehicles, maintenance and utility vehicles, and emergency vehicles. Strobe lights and flashing beacons also have stationary applications, such as on road signaling stands and warning signs, on the visual part of alarm systems, and on mining equipment. Strobe lights and flashing beacons provide visibility, as well as alert people to potentially dangerous situations.
Operationally, flashing lanterns require circuitry that will produce a rapid-rise-time light pulse in order for the lantern to be capable of flashing frequently and distinctly in a given time interval. The flash must also be sufficiently intense to meet the requirements of the intended lighting conditions (full daylight to complete darkness). Further, flashing lanterns must be reliable in harsh weather conditions and, when used on moving objects, flashing lanterns must be vibration resistant. Lastly, it is usually beneficial if the light emitted by a flashing lantern is visible from all sides of the lantern.
Conventional flashing lanterns comprise a flash element or light source, a control circuit, a power source, a base, and a housing. The control circuit produces the fast-rise-time pulse that controls the application of power to the flash element. The power source may be either internal to the lantern housing or external to the lantern housing. The power requirements can range from 12 to 48 volts DC. Suitable power sources are car batteries and portable generators.
The housings of flashing lanterns may include a lens configured to magnify the light emissions therefrom. For example, some flashing lanterns include a fresnel-type lens. While the direction of light emission through the lens is usually outward in a 360-degree arc, some flashing lanterns include diverters that direct emissions along a particular emission path.
In conventional flashing lanterns, the flash element or light source is typically an incandescent bulb or a xenon flash tube. Both types of light sources are the primary cause of lantern failures. In particular, incandescent bulbs have a tendency to burn out due to their wires and filaments becoming brittle with age or weak due to external lantern vibrations. Therefore, incandescent bulbs have a relatively short life. Replacement of incandescent bulbs normally requires some disassembly and, thus, is more expensive and time consuming than desirable. Further, incandescent bulbs utilized in flashing beacons are normally not as bright as desired.
There are also many disadvantages to strobe lights. Xenon flash tubes require high operating voltage, produce UV radiation, and have an operating lit of only 2,000 to 3,000 hours. The high voltage requirements make the design of strobe lights more complicated than desired and can create a safety hazard, due to the possibility of an electrical shock during maintenance.
Lastly, with regard to both flashing beacons and strobe lights, neither produce monochromatic light. Color filters or lenses are required in order to provide colored light emission. Color filters or lenses decrease light transmission and often fade due to weathering and ultraviolet irradiation.
In recent years, a variety of attempts have been made to use LEDs as a light source in flashing beacons. At least four major types of LEDs are available, two of which are typically used in visible light devices--planar and dome LEDs. Due to their structure, the light produced by LEDs changes rapidly in intensity in response to a rapid change in current. LEDs are monochromatic and available in a variety of colors. Thus, using LEDs as a light source eliminates the need for colored filters or lenses, thereby optimizing light transmission while at the same time eliminating the problem of lens or color filter fading. LEDs require low power to operate and have a long operating life--over 100,000 hours for some types.
Although the above characteristics are advantageous commercially, early versions of LEDs had low light-emitting energy and luminance, which made them difficult to see. LEDs have also been difficult to utilize in flashing lanterns due to their inherent structure. More specifically, since the light emission path of a flashing lantern optimally covers an arc of 360 degrees, it is desirable to use an omnidirectional light source placed in the center of the lantern. Bulbs are omnidirectional; LEDs are not. In this regard, LEDs are typically created using flat semiconductor materials, resulting in a light emission path that radiates outwardly from a flat semiconductor plane. It is easier to see an LED looking at it straight on than looking at it from an angle. Therefore, prior art lanterns using LEDs often place the LEDs in a circle, so that the LED light will project outward in a 360-degree range.
One example of such a lantern is disclosed in U.S. Pat. No. 5,224,773 (Arimura) discloses a flashing lantern designed to compensate for the low luminance and poor side visibility of LEDs. Arimura uses a multitude of LEDs arranged about a cylindrical support member. The LEDs project radially from the periphery of the support. This arrangement compensates for the low side visibility of LEDs. The entire support is housed within a magnifying fresnel-type lens that further distributes the light emitted by the LEDs. In order to increase the luminance of the lantern, alternative embodiments are shown that contain multiple layers of LED tings. The result is a complex lantern configuration containing a multitude of LEDs. In addition, the light produced in any one direction is only produced by a few LEDs and, therefore, is not very bright.
Recent improvements in LED technology have resulted in the creation of LEDs having significantly increased luminance. The increased LED luminance decreases the need for a large number of LEDs to produce the high amount of light required of a flashing lantern. Although even modem LEDs do not produce enough light for a single LED to be used in a flashing lantern, it is now possible to produce flashing lanterns with fewer LEDs than in the past. The present invention is directed to providing such a flashing lantern.